How to Close Sqlite Connection without explicitly calling Close Method using .NET

Keeping the connection open for the lifetime of your application is not a good way to go.
I suggest to not follow this route.
On the contrary, I will try to encapsulate the functionality to attach a database inside a method that could be called on the need to use basis.

For example:

private static void AttachDB(string fileDB, string aliasName, SQLiteConnection cn) {     string sqlText = string.Format("ATTACH '{0}' AS {1}", fileDB, aliasName)     SQLiteCommand cmd = new SQLiteCommand(sqlText, cn)     cmd.ExecuteNonQuery(); } 

then in your code

using(SQLiteConnection cn = new SQLiteConnection(GetConnectionString())){     AttachDB(@"C:\SQLite\UserData.sqlite3", "UserData", cn);     // Do your code here} 

Close should not disconnect your database but this will only work when .NET connection pooling mechanism is on. Make sure you have that enabled in your connection string:

Data Source=filename;Version=3;Pooling=True;Max Pool Size=100;

Depending on how your class is defined, you can use Dispose or a destructor. Or, explicitly call Close() at the end of the program (from within Main, after Run...).